The architecture of complexity: A new blueprint

The logic of scientific discovery is now a concern of computer scientists, as well as philosophers. In the computational approach to inductive inference, theories are treated as algorithms (computer programs), and the goal is to find the simplest algorithm that can generate the given data. Both computer scientists and philosophers want a measure of simplicity, such that simple theories are more likely to be true than complex theories. I attempt to provide such a measure here. I define a measure of simplicity for directed graphs, inspired by Herbert Simon's work. Many structures, including algorithms, can be naturally modelled by directed graphs. Furthermore, I adapt an argument of Simon's to show that simple directed graphs are more stable and more resistant to damage than complex directed graphs. Thus we have a reason for pursuing simplicity, other than purely economical reasons.This paper is based on part of my doctoral dissertation. Thanks to my thesis supervisor Professor Alasdair Urquhart for his encouragement, constructive criticism, and for directing me to several relevant articles; to my advisor, Professor Ian Hacking, for reminding me to concentrate on results that might have some application in the real world; to Professor Eric Mendelsohn for checking my use of graph theory; and to my friend Wendy Brandts for sharing her ideas on a closely related problem.Thanks to my friends and family (the latter being a (proper) subset of the former, and both including Dr. Louise Linney, of course) for ongoing support in my scholastic endeavors.Thanks to the Social Sciences and Humanities Research Council for financial assistance. (Awards 452-86-5885 and 453-87-0513.) Thanks to the University of Toronto for financial assistance.     

Are words represented by nodes?

Semantic priming in a lexical decision task was investigated with concurrent pretarget and posttarget primes. The posttarget prime also served as a pattern mask of the lexical decision target. Forward priming is defined as the presence of a semantically related pretarget prime and an unrelated posttarget prime. Backward priming is defined as the presence of a semantically related posttarget prime and an unrelated pretarget prime. Forward and backward priming were compared both when the nonword foils were "legal" and when they were "illegal" with respect to English orthography. Predictions were derived for two general approaches to word recognition: spreading-activation and expectancy-set theories. Both approaches assume that word representations occupy distinct, nonoverlapping locations in memory. Backward-prime facilitation was equivalent to forward-prime facilitation when nonword foils were illegal; however, backward-prime facilitation was not significant when nonword foils were legal. These results challenge both approaches. The proposed solution uses semantic-space (distributed) representations that are functionally unitized by a resonant matching (verification) process.     

Generativity and Erikson's “belief in the species”

Generativity is the concern for guiding and promoting the next generation through such creative behavior as parenting, teaching, mentoring, leading, and generating products and outcomes that benefit others. Erikson (1963) has argued that in order to be generative in adulthood, people must have a fundamental “belief in the species” or a faith that human progress is possible and worth working toward. The present study focuses on hope and trust concerning the self and others (Erikson's “belief in the species”). In addition, however, the study examines the relation between generativity and personality traits, in this case, dominance, leadership, self-absorption, and nurturance. A sample of 70 adults was administered (1) a series of self-report questionnaires converging on Erikson's idea of belief in the species, (2) a self-report scale assessing generativity, (3) measures of personality traits, and (4) two open-ended measures of generativity requiring subjects to describe life commitments and creative endeavors. The results provide modest support for Erikson's claim of a link between belief in the species and generativity, with significant positive correlations obtained (1) between self-report generativity and two measures of belief in species and (2) between generativity assessed through life commitments and one measure of belief in the species. In addition, the personality trait of nurturance was positively related to all three generativity measures. Problems and issues in the assessment of generativity are discussed.     

Age differences in the acculturation process

Age differences were assessed in a conceptual model that seeks to explain how acculturation affects psychological well-being among Mexican Americans. The data were from a national probability sample of 859 persons of Mexican decent. It was hypothesized that low acculturation creates financial stress. Moreover, low acculturation and financial stress were in turn predicted to erode feelings of personal control and self-esteem. Finally, diminished feelings of control and low self-esteem were hypothesized to exert a negative impact on psychological well-being. When data from respondents of all ages was assessed, empirical support was found for all of the hypotheses except the linkage between acculturation and financial stress. However, few age differences emerged in the model. The authors conclude that older Mexican Americans may not be more vulnerable to the stressors associated with acculturation.     

Cognitive guidelines for simplifying medical information: Data framing and perception

In this paper, 1 describe psychological guidelines for simplifying medical information — methods to aid the perception and recognition of abnormalities in medical test reports. These techniques resemble natural human editing strategies outlined in prospect theory. The methods pre-edit data as humans do but to reduce human effort. I review empirical studies assessing these techniques and discuss needs for further research.     

Psychological conceptions of randomness

This article presents a critique of the concept of randomness as it occurs in the psychological literature. The first section of our article outlines the significance of a concept of randomness to the process of induction; we need to distinguish random and non-random events in order to perceive lawful regularities and formulate theories concerning events in the world. Next we evaluate the psychological research that has suggested that human concepts of randomness are not normative. We argue that, because the tasks set to experimental subjects are logically problematic, observed biases may be an artifact of the experimental situation and that even if such biases do generalise they may not have pejorative implications for induction in the real world. Thirdly we investigate the statistical methodology utilised in tests for randomness and find it riddled with paradox. In a fourth section we find various branches of scientific endeavour that are stymied by the problems posed by randomness. Finally we briefly mention the social significance of randomness and conclude by arguing that such a fundamental concept merits and requires more serious considerations.     

Memories of a bicycle tour

One person's memories of a 47-day bicycle tour of Scandinavia were tested 3–4 months later. The tests assessed frequency, spatial, and temporal knowledge of events. Results indicated that frequency judgements were based on some combination of counts of discrete event memories and a general impression of the tour. Episodic memories showed clear variation as a function of where events had occurred, and judged and actual locations of episodes were strongly related. In fact, knowledge of the week in which something had happened appeared to hinge on where in a sequence of locations it was thought to have taken place. The apparent dependence of temporal judgements on spatial information is consistent with other findings in the literature indicating that temporal memories about past events are derived from a variety of other associated information, much of which is temporally referenced.     

Covert visual orienting: Hemifield-activation can be mimicked by zoom lens and midlocation placement strategies

How is attention distributed over visual space when an observer expects a target to occur at one of several possible locations? Two experiments sought to understand the source of the conflict between studies leading to the notions of hemifield activation (Hughes and Zimba 1985) and attentional gradients (Downing and Pinker 1985; Shulman et al. 1985, 1986). Subjects were cued to attend one of the 4 corners of an imaginary square centered at fixation, allowing comparison of uncued locations in the cued and uncued hemifields. In one experiment marking of the 4 locations was varied to determine if providing a ‘target’ for attention is necessary to obtain within-hemifield gradients. RT was faster at the cued location than at the three uncued locations which had equivalent latencies, a pattern that was unaffected by marking of the potential target locations. This result, which is consistent with the notion of a gradient around the attended location is a strong disconfirmation of the hemifield activation hypothesis. The second experiment demonstrated that an unusual procedure for presenting the probe stimuli in Hughes and Zimba (1985) is at least partially responsible for their evidence for uniform hemifield activation. It is proposed that visual attention is directed to visuo-spatial channels with fixed structural properties, and that when attention to two locations is desired, the subject may attend a spatial channel located between them.